A flexible-fuel vehicle (FFV) vehicle is a vehicle that can alternate between two or more sources of fuel. A common example is a vehicle that can accept gasoline mixed with varying levels of bioethanol (gasohol). As another example, some vehicles carry a natural gas tank, and can switch from gasoline to natural gas. The natural gas is stored as either compressed natural gas (CNG) or liquefied natural gas (LNG). Vehicles designed to run on either of two fuels are also referred to as “dual fuel” vehicles.
In North America, vehicles from approximately 1980 onward can run on 10% ethanol and 90% gasoline (referred to as E10 fuel) with no modifications. To use more than 10% ethanol, a vehicle generally requires special engineering. In the United States, many flexible-fuel vehicles can accept up to 85% ethanol (E85) or up to 85% methanol (M85).
As of the last several years, most existing vehicles that are available to the public with flex-fuel engines are sport-utility vehicles or others in the “light truck” class. Sedans, wagons, and others are usually only available in flexible-fuel configurations as part of fleet vehicle purchases. In the near future, more widespread availability is planned for standard models.
Flexible-fuel vehicles are in wider use abroad. For example, since the oil crisis in the 70's, Brazil has been selling ethanol as an automotive fuel. Cars in Brazil can run with arbitrary combinations of gasoline and alcohol (up to 100% of alcohol), but cannot use pure gasoline—they are optimally designed to run on gasoline mixed with 20% to 25% of ethanol. In European countries, there are also plans of selling E85 fuel as well as flexible-fuel vehicles.